1. Field of the Invention.
This invention relates to an improved drilling process wherein the drilling fluid contains water, surfactant, hydrocarbon, and optionally cosurfactant and/or electrolyte. Lamellar micelles are present in the composition.
2. Description of the Prior Art.
Zlochower and Schulman, in the Journal of Colloid and Interface Science, Vol. 24, No. 1, May, 1967 pp. 115-124 defines a liquid crystal obtained from a composition consisting of amino methyl propanol and amino butanol oleate microemulsions of water and benzene. The initial solution, i.e., before the liquid crystal, is an isotropic solution consisting of spherical micelles of decyl trimethylammonium bromides--chloroform in water. This is titrated with chloroform to form the liquid crystal and upon further addition of the chloroform, a second isotropic solution is formed with the chloroform as the external phase.
Canadian Pat. No. 921,690 teaches an oil recovery process using a micellar system containing 2-16% surfactant, 3-20% hydrocarbon, 1-5% alcohol and the residue water which exhibits birefringence, shear thickening behavior at low shear rates and shear thinning behavior at high shear rates, etc. These systems do not exhibit retro-viscous properties as do applicants' compositions.
Both oil-external and water-external micellar dispersions (this term includes microemulsions, micellar solutions, etc.) are described in the art, e.g., see U.S. Pat. Nos. 3,254,714 to Gogarty et al.; 3,497,006 to Jones et al.; 3,506,070 and 3,507,071 to Jones. The dispersions contain petroleum sulfonates (average equivalent weight = 350-525), hydrocarbon, water, cosurfactant (can be alcohol, etc.) and/or electrolyte. These dispersions generally exhibit a decrease in viscosity upon increase in flow rate.
U.S. Pat. No. 3,734,856 to Son, Jr. teaches using a micellar dispersion as a drilling fluid. The dispersion contains 10-95% hydrocarbon, 5-40% petroleum sulfonate having an average equivalent weight of 350-520, and sufficient water to obtain a desired viscosity. Electrolytes and/or cosurfactants can be incorporated into the dispersion.